This invention relates generally to valve structures and means to effectively seal such valves against leakage and more particularly to such valves for use with flowing cementitious materials having both fine and course granular constituents which subject parts in the flow path to abrasive wear and tear.
One of the primary problems encountered in valves used in regulating the flow of pressurized, cementitious type materials is providing means which will effectively seal the valve against leakage of water from the cementitious material contained in the supply line when the valve is in the off position, which may prevent the resumption of flow when the valve is again turned to an open position, as the water also serves as a vehicle for assisting in the flow of the cementitious material. This phenomena is similar to that which occurs when the water is squeezed out of a handful of damp sand. Another problem is to provide such sealing means which will resist the extremely abrasive conditions created by the presence of the cementitious material, thereby affording reasonably long life span. Ordinary sealing means, which are generally in the form of rubber or other resilient materials commonly used to seal valves, are not satisfactory when used in valves through which pressurized concrete or other cementitious type materials are flowing as the abrasive nature of these materials increases the wear on these seals to the point that the life span of the seals is reduced to an unexceptable level. In addition to the abrasive wear, the concrete has a tendency to accumulate on the seals, set up, and thereby cause portions of the seals to break or chunk away when the valve is operated.
Accordingly, the present invention provides a unique sealing arrangement which overcomes these problems by providing a valve core which has a minimum clearance to the valve housing thereby excluding all but the smallest abrasive particles. The valve is then sealed against the leakage of even these small particles, as well as water, through the combination of a pair of O rings providing axial seals and bar seals extending between these O rings which prevent circumferential leakage. The bar seals are retained in the grooves provided on either the outer surface of the core or the inner surface of the valve housing and are comprised of a rectangular or square cross section bar or core member having resilient material secured thereto on three of its sides. This resilient material, being of a slightly greater thickness on the bottom, serves to urge the exposed side of the core member out of the groove and into sealing engagement with the opposing metal surface of the valve body or core. The bar seal also provides a wiping action as the valve is operated thereby minimizing the build-up of cement film occurring along the opposing metal surface thereof, which may adhere and eventually prohibit the valve from opening. A further advantage of major importance of this metal core type bar seal is its ability to resist outward deformation as the center portion of the seal passes over an inlet or outlet port which, if not restrained, could result in the outer portions of the resilient material being sheared off as the valve is operated. Typically, the metal core will limit this deflection to a maximum of about 0.001 inch.
Additional features and advantages of the present invention will become apparent from the following detailed description of the preferred embodiment taken in conjunction with the drawings.